Li Yuanying was stubborn, and Li Shimin indulged him and acquiesced in his behavior. As long as it does not threaten his throne, let him do whatever he wants. Wherever Li Yuanying goes, people there will have a hard time. Because Li Yuanying has a bad personality, he loves beauty and gold and silver jewelry. The emperor is his brother, and he naturally does whatever he wants.
Li Shimin assigned Li Yuanying to Shandong, but why did Li Yuanying increase taxes for its own enjoyment, which made people complain. Li Shimin was speechless, too, and transferred him to other places. Who knows that he is still a leopard cannot change his spots, and he still goes his own way, and the people have great opinions.
Li Yuanying also fell in love with other people's wives and tricked people into their own homes. This woman has some martial arts skills and gave Li Yuanying a good beating.
In my opinion, the reason why Li Shimin spared Li Yuanying in the change of Xuanwu Gate was not because of the so-called brotherhood, but because Li Yuanying's character was corrupt and there was no support in the DPRK. Li Shimin is very at ease with him, thinking that Li Yuanying will not pose a threat to himself. So Li Shimin is willing to indulge Li Yuanying all the time and let him go on like this.
In fact, Li Yuanying also has some advantages. Li Yuanying was so talented in painting butterflies that he even became a family. Li Shimin is very supportive of his interests.